Overspeed safety stop mechanism for engines



Oct. 30, 1934. e. 1.. LINDSAY OVERSPEED SAFETY STOP MECHANISM FOR ENGINES Filed Sept. 1, 1931 2 Sheets-Sheet l INVENTOR. George 1. Lino 5a] A TTORNEY.

Oct. 30, 1934; G. L. LINDSAY 1,973,951

OVERSPEED SAFETY STOP MECHANISM FOR ENGINES Filed Sept. 1. 1931 2 Sheets-Sheet 2 INVENTOR. 520/92 1 1 mafia ATTORNEY.

Patented Oct. 30, 1934 UNELTES STATES PATENT OFFEWZ OVERSPEED SAFETY STOP MECHANISM FOR ENGINES Application September 1, 1931, Serial No. 560,565

1 Claim.

This invention relates to engines of the internal combustion type and more particularly to safety stop mechanism arranged to function when a predetermined speed is attained or exceeded, especially in case of failure of the usual control mechanism or even of the speed governor.

One object of the invention is to provide safety stop means having but few simple parts which are cheap to manufacture and to assemble but positive in its operation. Another object is to arrange for close adjustment over a wide range of speeds. Still another object is to indicate at a glance the condition of the stop mechanism. Still another object is to provide for quick resetting of the mechanism after its actuation. Still other objects will be apparent from the detailed description which follows.

In order to illustrate the invention one concrete embodiment thereof is shown in the accompany- 20 ing drawings, in which:

Fig. 1 is a side elevational view of an internal combustion engine equipped with the invention;

Fig. 2 is a left-end elevational view of the englne;

Fig. 3 is a plan view on an enlarged scale of the stop mechanism, the lid of the casing having been removed to show the operating parts which are in their normal running position;

Fig. 4 is a plan view similar to Fig. 3 showing the position of the parts at the instant before the stop mechanism operates;

Fig. 5 is a View similar to Figs. 3 and 4 showing the position of the parts after the stop mechanism has operated;

Fig. 6 is a vertical sectional view showing the stop mechanism parts substantially on the line 66 of Figs. 3 and 1;

Fig. 7 is a fragmentary sectional view corresponding to the right-hand side of Fig. 6 but showing the parts after operation of the stop mechanism;

Figs. 1 and 2 disclose the invention as applied to an internal combustion engine indicated more or less diagrammatically at A and provided with an electrical ignition system which may include magneto a. The engine is equipped with a safety governor a of any suitable or desired type which may be mounted in a totally enclosed casing as indicated. The engine may be provided with a so conventional control wheel at a for manually controlling the starting, running and stopping of the same.

The present invention comprises a device intended to protect the engine A from damage due to excessive speed caused by failure of the speed governor a, or of the carbureting apparatus, or of the mixing valve linkage (if it be a gas engine), or of other parts. By preference the safety mechanism stops the engine by short circuiting the ignition system at any predetermined speed. While it may be mounted at any desired position upon the engine, it is herein shown as secured to the top of the casing of the speed governor mechanism a as in a casing 8 secured in place as by bolts 9 (Figs. 6 and 7). Casing 8 has a top plate 10 secured to the casing by machine screws 11. An insulator bushing 12 extends through plate 10 and carries binding post 13, which is connected by an insulated cable 14 to the primary circuit of magneto a, or to the low tension side of the coil in case a battery ignition system is used. A plunger 15 for grounding contact 13 is slidably mounted immediately beneath the latter in a bore 312 in casing 8, which bore has a reduced extension forming a shoulder which provides a fixed seat for a coil spring 16 acting on plunger 15. Plunger 15 has a stem 1511 which extends through the reduced portion of the bore 8a for a purpose presently to be described.

A release lever 17 is mounted within casing 8 for swinging movement about pivot pin 18 and provides a portion 17a adapted to be interposed between plunger 15 and binding post 13 to hold the former out of engagement with the latter. A reset handle 1% extends from lever 17 through slot 8b in casing 8. The offset end of lever 17 forms a nose 170 which overhangs a circular depression 80 in casing 8. Mounted in depression 80 is a rotary member or turn table 19 having a stud or pedestal 19a extending through registering openings in the bottom of casing 8 and top of governor casing 8 to secure the said turn table 19 to some rotating part of the engine, in this instance the vertical governor shaft a To the top of turn table 19 is secured a movable weight or actuator 20 as by a fulcrum pin 21. Diametrically opposed is a fixed counterweight 22 fixedly secured to turn table 19 as by rivets 23 so that approximate balance of the turn table is obtained at any speed. Weight 20 being movable is arranged to assume positions in equilibrium with centrifugal force through the action of a coil spring 24 secured to an extension or lug 20a on weight 20 as by an adjusting screw 25 and on its opposite end to a fixed post 26 on turn table 19. Point 2211 of fixed weight 22 serves as a stop for movement of actuator weight 20 under the action of spring 24 while post 2'7 serves as a stop when weight 20 is swung outwardly through the action of centrifugal force.

- 1 through the engine frame.

Fig. 3 shows the position of the parts when the engine is running at normal speeds. Weight 20 does not engage either stop 22a or stop 27 but is in a position of equilibrium therebetween, since centrifugal force, a function of the square of the speed, is balanced by the corresponding component of the tension of spring 24. At normal speeds the position or" movable weight 20 should correspond approximately to the position of fixed weight 22.

With an increase in speed, actuating weight 20 will swing outwardly as centrifugal force overcomes the tension of spring 24, as indicated in Fig. l, and by the time it engages stop 27, actuating shoulder 2022 will have been moved out far enough to contact with nose of lever 17 and knock the lever to plunger releasing position (Fig. 5). The device is made obsolutely positive in action by causing the weight to swing in a direction opposite to the rotation of turn table 19; the reaction of the blow, as shoulder 20b strikes nose 170, operating to assist centrifugalforoe in moving the weight outwardly.

Fig. 7 shows the position of the parts after the device has functioned to stop the engine. The actuating Weight 20 has knocked over the release lever 17 and allowed plunger 15 to move under the action of spring 16 into contact with binding post 13 thus short circuiting the ignition system The engine cannot now be started again until the safety stop mechanism has been reset by the operator. Resetting is accomplished by merely pulling down on stem 15a of plunger 15 and moving reset handle 17b of lever 17 back to its running position. A glance at the position of reset handle 171) will always tell the operator whether the machine has stopped on account of excessive speed or for some other reason. The device may be and should be tested occasionally by flipping the reset handle 171) with the finger to see if plunger 15 will make contact with binding post 13.

A wide range of adjustment of the safety stop mechanism is provided by adjusting screw 25. For best results'it should be set to operate just above the speed fixed by the conventional governor a when there is an instantaneous change from full load to no load. Breakage of any of the operative parts of the safety stop mechanism will cause the mechanism to function and stop the engine. Hence, if properly adjusted it will always be in operating condition.

I claim as my invention:

A centrifugal switch comprising a casing, a spring-actuated plunger mounted therein and adapted to control an electric circuit, a lever pivotally mounted in said casing and having a portion arranged for disposition over said plunger to maintain the latter in inoperative position,

a rotary member within said. casing, and means adjustably arranged on said member for actuation by centrifugal force at a predetermined speed of said rotary member to knock said lever outof plunger-holding position, said plunger and said lever havingv extensions projecting through openings in said casing to indicate the condition of said mechanism and to permit the same to be manually reset after operation.

GEORGE L. LINDSAY. 

